| With the rapid development of modern communication technology,the requirements for communication equipment are becoming increasingly demanding.Ultra-wideband(UWB)MIMO technology,with its advantages of wide bandwidth,high data rate,low power consumption,high channel capacity,and strong anti-interference ability,has become a common technology in modern communication technology.However,traditional RF communication systems often face the problem of large-sized filtering circuit components,which cannot satisfy the demand for miniaturization of communication equipment.By adding trap structures to the antenna,useless frequency signals can be filtered out,while ensuring the miniaturization of the equipment,thus having extremely high application value.This thesis focuses on the miniaturization,high isolation,and notch characteristics of UWB MIMO antennas,and has done the following work:First,a dual-notch UWB MIMO antenna based on polarization isolation was designed.By combining polarization isolation technology with a defect-ground decoupling network,high isolation between antenna elements is achieved.At the same time,by referring to fractal antennas,a two-branch structure is added to improve the wideband performance in some frequency bands.The overall size of the antenna is 26×26×1.6 mm~3,with a return loss less than-10 d B in the 3.0-11.8 GHz frequency band and isolation greater than 17 d B within the operating bandwidth.By using slotting technology,a S-shaped and U-shaped gap is etched on the surface to achieve dual-notch characteristics in the 5.1-6.1 GHz and 7.1-7.8 GHz frequency bands.Second,a dual-notch UWB MIMO antenna based on Vivaldi antenna was designed.Vivaldi antenna has wideband characteristics and can serve as an UWB MIMO antenna unit,contributing to miniaturization.The size of the antenna is only 26×22×1.6 mm~3,and a T-shaped groove is etched on the ground plane to reduce mutual coupling between antenna elements.The isolation is greater than15 d B within the operating bandwidth(3.1-11.8 GHz),and a U-shaped gap is etched on the ground plane and an SRR parasitic branch is loaded on the feed line to achieve filtering in the 5.8-6.4 GHz and 7.1-7.8 GHz frequency bands.Third,two dual-notch UWB MIMO antennas based on symmetric cutting were designed.By using symmetric cutting technology,half of the structure of a symmetric antenna is used as a MIMO unit to achieve miniaturization.The first antenna is a triple-notch UWB MIMO antenna,which introduces a F-shaped fence decoupling structure in the center of the ground plane to achieve high isolation within the operating bandwidth.The size of the antenna is 26×30×0.8 mm~3,the impedance bandwidth is 3.1-11.1 GHz,and an isolation greater than 20 d B is achieved within the operating bandwidth.The multiple-notch characteristics of the antenna are achieved by extending two ground plane branches on the ground plane and etching a L-shaped gap on the antenna surface,forming three stopbands in the 5.1-5.9 GHz,7.0-7.8 GHz,and 7.9-8.7 GHz frequency bands.The other antenna is a quad-port single-notch UWB MIMO antenna,which increases the number of antenna ports to improve MIMO system channel capacity.The antenna consists of four mutually orthogonal antenna elements and a metal shield decoupling structure to reduce antenna size and improve isolation.The size of the antenna is 45×45×0.8 mm~3,and the isolation within the working frequency range from 2.9-12.0 GHz reaches 15 d B,meeting the design requirements,with isolation as high as 20 d B in the 3.75-12.0 GHz frequency band.By using slotting technology,a L-shaped gap is etched on the surface of the antenna to achieve notch characteristics in the 5.1-6.0 GHz frequency band. |
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